SUMMARY Significance: Impaired alertness accompanied by short microsleep events is a frequently reported phenomenon in all areas of modem life. A microsleep event can be defined as a somewhat unexpected short episode of sleep, between 1 and 30 seconds, that occurs in the midst of ongoing wakeful activity. People who experience microsleeps usually remain unaware of them, instead believing themselves to have been awake the whole time. It is suspected that such microsleep events are responsible for many accidents on the road and in the workplace. Microsleeps become extremely dangerous when occurring during situations which demand continuous alertness, such as driving a motor vehicle or operating heavy machinery. Microsleep has a massive impact on health and safety. Today's toll of approximately 100,000 police-reported highway crashes with estimates of 1550 fatalities annually identified as having driver drowsiness/fatigue as principal casual factors. The onset of microsleep remains difficult to detect in real life settings. A used measure of drowsiness, so called `PERCLOS' ? the percentage of time a person's eyes are 80-100% closed over a period of time, typically five minutes. As such, it may detect only the very late stages of drowsiness and cannot timely detect onset of this dangerous subset of drowsy individuals. In this application we propose novel nondisruptive and nonintrusive technique to measure eyelid dynamic movement via assessment of related changes in the radio frequency of a very weak and totally harmless electromagnetic field created in the vicinity of the eyelids. Preliminary Data: Initial realization of this measurement technique was successfully demonstrated with the support from an award of National Science Foundation (NSF) for the project ?Fatigue Measurement Instrument?. The sensor created in that project included as a resonator - few turns of Teflon-coated very thin wire clipped to a frame resembling eyeglasses and connected to novel Eddy Current Inductance-to-Digital Converter LDC1000 microchip of Texas Instrument. Such very inexpensive (cost well below $100), high- resolution impedance measurement sensor could be worn (for example, as part of the required safety glasses in mining field) for a daylong assessment and recording of eyelid movement at any workplace without any interfering with an operator's everyday activity. Specific Aims: Develop signal analysis SW package for calculation of directly related to microsleep detection ocular variables: Amplitude-Velocity Ratio, i.e. the ratio of the maximum amplitude to maximum velocity of eyelid movement for the reopening phase of blinks; Percent Long Closures (%LC): proportion of time eyes are fully closed. Duration of Ocular Quiescence (DOQ). All these eyelid movement parameters will be measured during vigilance tasks following restricted sleep and a rested state to compare the measures to Oxford Sleep Resistance (OSLER) test at the Attention and Performance Lab of Washington University at St. Louis.